1. Field of the Invention
The present disclosure relates to methods and apparatuses for sound production, and in particular, to methods and apparatuses for producing sound at the ear of the user.
2. Related Art
FIG. 1 shows a diagram of a typical human ear. The outer ear, or pinna, is an irregularly concave cartilaginous member comprised of a number of eminences and depressions which give each ear a distinct shape and form. The helix 1100 is the curved outer rim of the ear; below the helix 1100 is the antihelix 1124, a curved prominence which describes a curve around the concha, a deep cavity containing the entry to the ear canal 1108. The concha is divided into two parts, the upper and lower concha 1128, 1132, by the crux of the helix 1104 which curves around the outside of the ear, and extends inwards at about the vertical midpoint of the ear. The upper concha 1128 lies above the crux of the helix 1104 and below the anti-helix 1124; the lower concha 1132 lies below the crux of the helix 1104 and surrounds the entry to the ear canal 1108. In front of the lower concha 1132 and projecting backwards from the front of the ear is the tragus, 1112 a small semicircular prominence. Opposite the tragus 1112 and separated from it by the deep curvature of the intertragic notch 1116 is the antitragus 1120.
FIG. 2 shows a typical earbud-type headphone 1200, hereinafter referred to as an “earbud.” The earbud 1200 is designed to rest snugly inside the ear canal 1108, at least where the ear canal 1108 opens into the lower concha 1132 or even deeper into the ear canal 1108, and is typically designed to fully occlude the ear canal 1108. A speaker (not shown) inside the earbud is typically positioned so as to direct sound waves 1212 directly into the ear canal and toward the middle ear 1216.
An earbud 1200 placed in the ear canal 1108 in this manner has a number of disadvantages.
First, it is noted that such an earbud 1200 creates an unhealthy amount of sound pressure on the middle ear 1216. In particular, not only does the speaker direct sound at the structures of the middle ear, but sound pressure waves reflected inside the ear have nowhere to escape, and continue to echo inside the ear canal 1108 and can repeatedly strike the middle ear 1216. Not only is this unhealthy, but it further creates unintended sounds and sound effects which reduce the quality of audio production.
Second, such an earbud 1200, by fully occluding the ear canal 1108, blocks outside sounds 1204 from entering the ear. This presents a safety risk, as important outside sounds such as traffic sounds and emergency alarms can not be heard when the earbuds 1200 are in use.
Third, such an earbud 1200 is necessarily uncomfortable to a large number of users, since ear canal diameter varies from individual to individual in a large way, while earbuds are often sold in only one or two sizes.
Finally, such an earbud 1200 makes no use of the unique curves and folds of the pinna, which are used in day-to-day hearing to identify sources of sounds, to help separate high and low frequency sounds so that the structures of the inner ear can better distinguish between the two, and to generally form what the typical listener has come to identify as a “realistic” sound. By directing sound linearly into the ear canal 1108, such an earbud 1200 creates an undesirably artificial sound.
It should be noted that other headphones, such as earmuff-style headphones or earcap-style headphones, pose similar disadvantages, including at least full occlusion of the ear canal, an echo surface for sound waves which are reflected at the middle ear, and the unhealthy aiming of sound waves directly at the structures of the middle ear.